Method for designing a stator segment for a stator of a synchronous reluctance machine and corresponding stator and corresponding reluctance machine

Abstract

The disclosure relates to a method for designing a stator segment for a stator of an m-phase synchronous reluctance machine with concentrated windings, the stator being divided into a stator segment or a plurality of stator segments and comprising a ferromagnetic base body with peripherally distributed tooth structures and a winding system mounted in the base body, which comprises, per stator segment, z tooth structures and a number of winding phases (U, V, W) corresponding to the number of phases m, each of said winding phases comprising a series connection and/or a parallel connection of a plurality of the concentrated windings, a rotor of the synchronous reluctance machine comprising a pole number p in a peripheral section corresponding to the stator segment.

Claims

1. Method for designing a stator segment for a stator of an m-phase synchronous reluctance machine with concentrated windings, wherein the stator is capable of being divided into a stator segment or into a plurality of stator segments and comprises a ferromagnetic base body with peripherally distributed tooth structures and a winding system mounted in the base body, which has z tooth structures and a number of winding phases (U, V, W) corresponding to the number of phases m per stator segment, wherein each of the winding phases in turn comprises a series and/or parallel connection of a plurality of the concentrated windings, wherein a rotor of the synchronous reluctance machine has a pole number p in a peripheral section corresponding to a stator segment, the method comprising: selecting a stator tooth number z of the tooth structures in a stator segment depending on the phase number m of the phases (U, V, W) and the pole number p; determining a winding factor F.sub.W and a torque factor F.sub.T with $F_T=1-{\int }_0^{2\pi \text{/}K}{\left(\frac{\left[\mathrm{MMF}\left(\theta \right)-H_P\left(\theta \right)\right]}{\mathrm{MMF}\left(\theta \right)}\right)}^{2}d\theta$ for a plurality of design and arrangement options for the winding phases (U, V, W), which result from a given variables pole number p and number of phases m when using concentrated windings with respect to the stator tooth number z, wherein θ is an angle in a stator rotation direction, MMF is a measure for a spatial distribution of an electric loading, H.sub.P is a harmonic amplitude respectively over the angle θ and K is a division factor indicating a proportion of the stator segment in a total periphery of the stator; and determining at least one design of the stator segment in which a formula product of winding factor and torque factor F.sub.T.Math.F.sub.W has a local maximum.

2. Method according to claim 1, wherein the plurality of design and arrangement options of the winding phases (U, V, W), for which the winding factor F.sub.W and torque factor F.sub.T are determined, is covered by varying the number of windings and/or a distribution of these windings over the tooth structures of the stator segment.

3. Method according to claim 1, wherein per tooth structure a single winding or a plurality of windings are provided.

4. Method according to claim 1, wherein for systematically going through a design and arrangement options of the winding phases (U, V, W) the tooth structures are divided into a plurality of levels with respect to their tooth height; a tooth-specific winding is assigned to each tooth structure on each of the levels (E1, E2), so that the same sequence of windings is obtained on each level (E1, E2); the windings are connected to the winding phases (U, V, W); and positions of the windings are permuted by level-wise shifting a sequence with respect to the tooth structures.

5. Method according to claim 1, wherein a selection of at least one design of the stator segment is done depending on a size of the torque factor F.sub.T.

6. Method according to claim 5, wherein the selection of at least one design is done only for a stator tooth number z of the tooth structures per stator segment which is smaller than a product of the number of phases m and the pole number p, which means z<m.Math.p.

7. Method according to claim 1, wherein the winding factor F.sub.W is determined and/or individually calculated from existing data sets.

8. Method according to claim 5, wherein a selection of at least one design of the stator segment is done only for a torque factor F.sub.T≥0.5.

9. Stator for an m-phase synchronous reluctance machine with concentrated windings which is capable of being divided into one stator segment or into a plurality of stator segments and which comprises a ferromagnetic base body with peripherally distributed tooth structures and a winding system mounted in the base body, which comprises per stator segment a number of tooth structures corresponding to a stator tooth number z and a number of winding phases (U, V, W) corresponding to the number of phases m, wherein each winding phase in turn comprises a series connection of a plurality of twelve concentrated windings, wherein a rotor of the synchronous reluctance machine has a pole number p in a peripheral section corresponding to a stator segment, wherein the number of phases m=3, the pole number p=10 and the number of stator teeth is 18, wherein the series connection of the plurality of twelve concentrated windings has the following winding scheme with respect to a phase-specific first tooth structure position: a first and a second winding at a first position, a third winding at a third position, a fourth winding at a sixth position, a fifth and a sixth winding at an eighth position, a seventh and an eighth winding at a tenth position, a ninth winding at a twelfth position, a tenth winding at a fifteenth position and an eleventh and a twelfth winding at a seventeenth position.

10. Stator according to claim 9, wherein the tooth structures are divided into a plurality of levels (E1, E2) with respect to their tooth height, wherein the same sequence of windings is achieved on each level (E1, E2), wherein the sequence of one of the levels (E1) is offset from the sequence of at least one of the other levels (E2) by at least one tooth structure.

11. Synchronous reluctance machine with concentrated windings, comprising a stator and a rotor, wherein the stator is configured according to claim 10.

12. Stator according to claim 10, wherein for each of the three winding phases (U, V, W) the first winding, the second winding, the fifth winding, the sixth winding, the ninth winding and the tenth winding are wound in one orientation around the respective tooth structure; and the third winding, the fourth winding, the seventh winding, the eighth winding, the eleventh winding and the twelfth winding are wound in an opposite orientation around the respective tooth structure.

13. Stator according to claim 9, wherein for each of the three winding phases (U, V, W) the first winding, the second winding, the fifth winding, the sixth winding, the ninth winding and the tenth winding are wound in one orientation around the respective tooth structure; and the third winding, the fourth winding, the seventh winding, the eighth winding, the eleventh winding and the twelfth winding are wound in an opposite orientation around the respective tooth structure.

14. Synchronous reluctance machine with concentrated windings, comprising a stator and a rotor, wherein the stator is configured according to claim 9.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) In the drawing:

(2) FIG. 1 is a schematic representation of a stator segment of a stator according to an embodiment of the disclosure.

DETAILED DESCRIPTION

(3) Here, a stator segment 10 of a stator 12 for a (m=3)-phase synchronous reluctance machine with concentrated windings and a rotor (not shown) is shown by way of example and in a non-restrictive manner, wherein in the example shown the 360° stator segment 10 corresponds to the stator 12. The stator segment 10 comprises a ferromagnetic base body 14 with eighteen peripherally distributed tooth structures 16 and a winding system 18 mounted in the tooth structures 16 of the base body 14. The stator segment comprises z=18 tooth structures and a number of 3 winding phases U, V, W corresponding to the number of phases m=3, wherein each winding phase in turn comprises a series connection and/or parallel connection of a plurality of the concentrated windings 20. Here, the stator 12 is provided for a synchronous reluctance machine whose rotor has a pole number p=10 in a peripheral section corresponding to the stator segment (not shown).

(4) Thus, a corresponding “18-10 winding scheme” is achieved in which the three winding phases U, V, W are offset from one another respectively by six tooth structures 16. Each of the three winding phases U, V, W comprises a series connection of twelve concentrated windings 20 which with respect to a phase-specific first tooth structure position 22, 24, 26 has the following winding scheme: first and second windings at said first position, third winding at the third position, fourth winding at the sixth position, fifth and sixth windings at the eighth position, seventh and eighth windings at the tenth Position, ninth winding at the twelfth position, tenth winding at the fifteenth position and eleventh and twelfth windings at the seventeenth position.

(5) Here, for each of the three winding phases U, V, W: the first winding, the second winding, the fifth winding, the sixth winding, the ninth winding and the tenth winding are wound in a first orientation around the respective tooth structure and the third winding, the fourth winding, the seventh winding, the eighth winding, the eleventh winding and the twelfth winding are wound around the respective tooth structure in an opposite second orientation.

(6) If the stator is divided into a plurality of segments this scheme is achieved over all segments in a peripheral direction which is indicated in FIG. 1 by the direction of the arrows.

(7) At the phase-specific seventeenth (tooth structure) position, the respective winding phase U, V, W is fed out of the ferromagnetic base body. Here in this example, the fed out ends of the winding phases U, V, W are connected to a star point 28.

(8) The 3-phase synchronous reluctance machine thus has the following variables: eighteen tooth structures, ten poles (=five pole pairs), winding system as a 4-layer winding with an offset (shift) by 7 teeth (per phase). FIG. 1 shows the corresponding 18-10 winding scheme.

(9) Here, a torque factor of 0.75 can now be achieved. Together with the winding factor of 0.735 the machine achieves a total factor of:
F=F.sub.T.Math.F.sub.W=0.735.Math.0.75=0.55

(10) The exemplary machine with 18 teeth and 10 poles can also be operated in a series connection as a 3-layer machine without leaving the effective range of the optimized design.

(11) Further details and advantages of the disclosure are described in other words below.

(12) During the assembly the stator is wound with concentrated, non-overlapping windings (tooth coils). For this purpose, the winding can be implemented in multiple layers. The winding can be used for round, closed machines as well as for machine segments and linear motors. In order to generate a magnetomotive force MMF with reduced spatial harmonic components, which lead to a high torque density and a good power factor, in contrast to the state of the art two factors have to be applied in the machine pre-design, wherein the first one considered individually is known in principle and only allows a useful motor design for tooth coils in the second subsequent step. 1.) Pre-design based on the winding factor F.sub.W: known in the literature and can be read out from tables or calculated for any stator tooth/rotor pole combination; 2.) Pre-design according to the torque factor F.sub.T: this newly defined factor enables the calculation of the magnetic utilization of a rotor pole.

(13) As previously explained in detail, it is generally known in the literature that synchronous reluctance machines with concentrated windings are difficult or impossible to implement. This is mainly due to the poor torque factor F.sub.T for conventional concentrated windings. The factor applies to motors with permanent magnets, synchronous reluctance machines as well as any combinations of permanent magnet and reluctance motors. The calculation of the factor applies unchanged to permanent magnet synchronous machines and synchronous reluctance machines. The factor is calculated from the working harmonic MMF wave of the machine, which defines the pole number, and the total resulting MMF from all harmonic components that occur.

(14) The newly used torque factor required for targeted design can be methodically defined as follows:

(15) $F_T=1-{\int }_0^{2\pi \text{/}K}{\left(\frac{\left[\mathrm{MMF}\left(\theta \right)-H_P\left(\theta \right)\right]}{\mathrm{MMF}\left(\theta \right)}\right)}^{2}d\theta$

(16) Here, the MMF corresponds to the electromagnetic field distribution over the spatial angle. H.sub.P denotes the harmonic amplitude of the working wave, which defines the pole number of the motor. The factor is calculated via the integral of a stator revolution of the angle. The integral is determined from 0° to 360°/K. K corresponds to a division factor which describes the angle section which is covered by the pole number of the stator segment. For a fully loaded round machine, thus K=1.

(17) For concentrated windings, the factor is usually <0.4-0.7.

(18) If now a conventional concentrated winding with one or two levels is divided in a plurality of winding systems and arranged offset by x tooth structures (for x={1, . . . stator tooth number}) in 2 to i levels of 2−x winding systems with respectively one system, when using the evaluation method according to the embodiment of the disclosure and a specific arrangement an overall MMF with low harmonic components and a good torque factor F.sub.T are achieved. The inventors were able to discover in a surprising way on such designed machines that the total utilization of a machine is given by the product of the winding factor F.sub.W and the torque factor F.sub.T.

(19) By means of the design method according to the disclosure using these new finding it is possible in a simple way to design machines with high power density, good power factor and low torque ripple more purposefully and without iterative setbacks.

(20) In the following, the procedure according to the disclosure will now be described in more detail based on exemplary machine designs, however, it may be evident to the person skilled in the art to use the method for further machine designs in a different order or specification, which cannot be shown here by way of example but also result analogously within the scope of the method.

(21) Methodical Procedure According to the Disclosure:

(22) 1.) Definition of a first number of stator teeth depending on the desired number of phases or a rotor pole number depending on the pole width, the diameter and a desired rotational frequency (speed) of the machine. Here, a design in the range of 50 Hz, 60 Hz, as is customary for industrial machines, or even up to 1000 Hz is conceivable;

(23) 2.) Optimization of the formula product until a local maximum is determined over all variables. Here, the stator and rotor pole numbers can be changed again, in particular also the distribution of the coils, according to the disclosure with the variables: a. Offset by x teeth; b. Distribution of the windings N per tooth structure while optimizing the winding factor;

(24) 3.) Calculation of the factor according to the above information;

(25) 4.) Geometric pre-design of a bore volume based on the desired performance data and the use of an applied mean rotational shear density (e.g. 25 kN/m.sup.2); and

(26) 5.) Fine design by use of known methods, e.g. also with the aid of the methods of DOE (Design of Experiment) including a. fine design of the flow cross sections; b. fine design of the electric loading, the thermal utilization; and c. the amount of magnet in relation to the reluctance component.

(27) A tooth structure comprises a total of N windings, wherein for the division of the number of windings of the e.g. two windings per tooth N1 is equal to or may be N2 or N1 is not equal to or may not be N2. According to the manufacturing process for identical number of windings or even different number of windings other coil structures may be useful, so that an assembly can be achieved with an optimized degree of filling. Thus, conical or parallel coils can be installed alternately on the machine without interrupting the relationship according to the formula.

(28) According to the disclosure, all machines with a torque factor F.sub.T>0.5 and

(29) $q=\frac{\#\mathrm{stator}\mathrm{teeth}}{\#\mathrm{phases}.Math.\#\mathrm{rotor}\mathrm{poles}}<1$
are covered.

(30) The trivial case of the pure use of the reluctance force without magnetic material results in an unchanged applicability of the method.